Flavor learning and memory in utero as assessed through the changing pattern of olfactory responses from fetal to neonatal life

Mammalian chemosensory experience begins in utero, where fetuses are exposed to odors and tastes from the mother’s diet. Although the effects of prenatal flavor exposure in humans have been investigated postnatally in infant behaviors, longitudinal follow-up studies of fetal and neonatal responses are lacking. To address this, we compared fetal and neonatal facial reactions to specific odors by asking mothers to consume a single calorie-controlled encapsulated dose of powdered kale (n = 14) or a carrot (n = 18) before 4D ultrasound scans at 32 and 36 gestational weeks. Following the 36-week scan, mothers consumed the capsules daily for three consecutive weeks. Results indicated that neonates (mean age = 3.06 weeks) showed a decreased frequency of cry-face, and an increased frequency of laughter-face gestalts in response to the odor stimulus experienced prenatally, regardless of associated taste profile (bitter or non-bitter). These results suggest that repeated chemosensory experience in utero can reduce the aversive hedonic responses of fetuses and shape postnatal memory of the in utero experienced odor. This suggests that prenatal chemosensory mechanisms may have the potential to promote healthy eating habits after birth.